This invention relates generally to monitoring systems and, more particularly, concerns pressure-sensitive devices and systems used to monitor patients in hospital or other care giving environments.
It is well documented that the elderly and post-surgical patients are at a heightened risk of falling. There are many reasons for this but, broadly speaking, these individuals are often afflicted by gait and balance disorders, weakness, dizziness, confusion, visual impairment, and postural hypotension (i.e., a sudden drop in blood pressure that causes dizziness and fainting), all of which are recognized as potential contributors to a fall. Additionally, cognitive and functional impairment, and sedating and psychoactive medications are also well recognized risk factors.
A fall places the patient at risk of various injuries including sprains, fractures, and broken bonesxe2x80x94injuries which in some cases can be severe enough to eventually lead to a fatality. Of course, those most susceptible to falls are often those in the poorest general health and least likely to recover quickly from their injuries. In addition to the obvious physiological consequences of fall-related injuries, there are also a variety of adverse economic and legal consequences that include the actual cost of treating the victim and, in some cases, caretaker liability issues.
In the past, it has been commonplace to treat patients that are prone to falling by limiting their mobility through the use of restraints, the underlying theory being that if the patient is not free to move about, he or she will not be as likely to fall. However, research has shown that restraint-based patient treatment strategies are often more harmful than beneficial and should generally be avoidedxe2x80x94the emphasis today being on the promotion of mobility rather than immobility. Among the more successful mobility-based strategies for fall prevention include interventions to improve patient strength and functional status, reduction of environmental hazards, and staff identification and monitoring of high-risk hospital patients and nursing home residents.
Of course, monitoring high-risk patients, as effective as that care strategy might appear to be in theory, suffers from the obvious practical disadvantage of requiring additional staff if the monitoring is to be in the form of direct observation. Thus, the trend in patient monitoring has been toward the use of electrical devices to signal changes in a patient""s circumstance to a caregiver who might be located either nearby or remotely at a central monitoring facility, such as a nurse""s station. The obvious advantage of an electronic monitoring arrangement is that it frees the caregiver to pursue other tasks away from the patient. Additionally, when the monitoring is done at a central facility a single nurse can monitor multiple patients which can result in decreased staffing requirements.
Generally speaking, electronic monitors work by first sensing an initial status of a patient, and then generating a signal when that status changes, e.g., he or she has sat up in bed, left the bed, risen from a chair, etc., any of which situations could pose a potential cause for concern in the case of an at-risk patient. Electronic bed and chair monitors typically use a pressure sensitive switch in combination with a separate monitor/microprocessor. In a common arrangement, a patient""s weight resting on a pressure sensitive mat (i.e., a xe2x80x9csensingxe2x80x9d mat) completes an electrical circuit, thereby signaling the presence of the patient to the microprocessor. When the weight is removed from the pressure sensitive switch, the electrical circuit is interrupted, which fact is sensed by the microprocessor. The software logic that drives the monitor is typically programmed to respond to the now-opened circuit by triggering some sort of alarmxe2x80x94either electronically (e.g., to the nursing station via a conventional nurse call system) or audibly (via a built-in siren).
General information relating to mats for use in patient monitoring may be found in patent application Ser. No. 09/285,956 filed Apr. 2, 1999, now U.S. Pat. No. 6,307,476, the disclosure of which is specifically incorporated herein by reference. Additionally, U.S. Pat. Nos. 4,179,692, 4,295,133, 4,700,180, 5,600,108, 5,633,627, 5,640,145, and 5,654,694 (concerning electronic monitors generally) contain further information generally pertinent to this same subject matter, as do U.S. Pat. Nos. 4,484,043, 4,565,910, 5,554,835, and 5,623,760 (switch patents), the disclosures of all of which are all incorporated herein by reference.
By way of general background, in a typical arrangement, a pressure-sensing mat is a sealed xe2x80x9csandwichxe2x80x9d composed of three layers: two outer layers and an inner (central) layer positioned therebetween. The outer layers are usually made of some sort of plastic and are impermeable to fluids and electrically non-conductive on their outer faces, where xe2x80x9couterxe2x80x9d is determined with respect to the middle layer. The inner surface of each of the outer layersxe2x80x94which inner surfaces are oriented to face each other from opposite sides of the central layerxe2x80x94is made to be electrically conductive, usually by printing a conductive (e.g., carbon-based) ink on that surface. The compressible middle xe2x80x9ccentral spacerxe2x80x9d is made of a non-conductive material and serves to keep the two conductive faces apart when a patient is not present on the sensor. The central spacer is discontinuous, which makes it possible for the two conductive inner surfaces to be forced into contact through the discontinuities when weight is applied to the switch. By attaching a separate electrical lead to each of the conductive inner faces, it can readily be determined (e.g., via a simple continuity check) whether a weight is present on the sensor (e.g., whether a patient is seated thereon). Removal of the weight causes the central spacer to expand and press apart the two conducting faces, thereby breaking the electrical connection between them. Thus, a device that monitors the resistance across the two electrical leads may determine when a patient has risen to his or her feet.
One disadvantage of the current generation of pressure sensitive mats is that they cannot be completely (e.g., hermetically) sealed against the external environment. The reason for this should be clear: if the interior of the mat were completely sealed, air pressure inside of the mat would tend to oppose the urging of the mat faces into contact, thereby making it difficult or impossible to complete the circuit (e.g., think of compressing an xe2x80x9cair pillowxe2x80x9d). Thus, it is customary to intentionally leave gaps in the seal between the two halves of the mat which allow for movement of air into and out of the switch.
Another disadvantage of the prior art is that partial sealing of the perimeter of the mat can cause it to resist expansion after weight is removed therefrom. That is, when a patient places weight on a conventional mat, air is slowly expelled from the mat interior, typically through a small opening in the perimeter of the mat. However, when the patient rises the opening in the mat can collapse or narrow in response to air pressure on the now-deflated mat body, thereby retarding the process of reinflating it. As a consequence, the mat may continue to signal that the patient is still present on the mat for a time after he or she has risen.
Of course, the fact that the interior of the mat must kept open to the atmosphere results in a mat that is highly susceptible to invasion by bodily fluids or cleaning solutions, as the in-rushing air tends to carry fluids along with it into the interior of the mat. Further, it is well known that some common disinfecting cleaners can loosen the adhesives that hold the layers of the mat together, thereby ruining the sensor. Thus, cleaning soiled mats that have air passages placed therein becomes problematic. In summary, what is needed is a pressure sensitive mat that is more resistant to invasion by fluids than is presently available.
Heretofore, as is well known in the patient monitoring arts, there has been a need for an invention to address and solve the above-described problems. Accordingly, it should now be recognized, as was recognized by the present inventors, that there exists, and has existed for some time, a very real need for pressure sensitive mat and monitoring system that would address and solve the above-described problems.
Before proceeding to a description of the present invention, however, it should be noted and remembered that the description of the invention which follows, together with the accompanying drawings, should not be construed as limiting the invention to the examples (or preferred embodiments) shown and described. This is so because those skilled in the art to which the invention pertains will be able to devise other forms of this invention within the ambit of the appended claims.
In accordance with a first aspect of the instant invention, there is provided a pressure sensitive mat which has preferably been completely sealed around its exterior edges except where a breathing tube passes therethrough. The interior of the mat is kept in communication with the atmosphere by way, of a section of flexible tubing which encloses the attached electrical line. One end of the tubing is sealed inside of the mat and the other end is open to the atmosphere, thereby providing a passageway for air to reach the interior of the mat. This arrangement, however, protects the interior of the mat from exposure to fluids that might be present near its perimeter. In fact, this innovation allows the mat-portion of the invention to be completely submersed without adverse effect, if that should be come necessary.
According to another aspect of the instant invention, there is provided a pressure sensitive mat and breathing tube combination wherein the wires that transmit status information from the interior of the mat to a separate electronic monitor are not inside of the breathing tube, but instead are adjacent to it through at least part of their length. One example of such an arrangement would be found in a multi-lumen tube of the sort that are well known to those skilled in the medical arts, wherein the electrical wires are preferably placed in one tube (or lumen), with one or more other tubes being kept clear to permit the passage of air therethrough.
Finally, according to still another aspect of the instant invention, there is provided a pressure sensitive mat and breathing tube combination, wherein the breathing tube is completely separated from the electrical wires and separately penetrates the mat perimeter to reach its interior.
The foregoing has outlined in broad terms the more important features of the invention disclosed herein so that the detailed description that follows may be more clearly understood, and so that the contribution of the instant inventor to the art may be better appreciated. Although the instant invention will be described in connection with a preferred embodiment, it is to be understood that it is not intended to limit the invention to that embodiment. That is, the instant invention is not to be limited in its application to the details of the construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. Rather, the invention is capable of other embodiments and of being practiced and carried out in various other ways not specifically enumerated herein. Further, it should be understood that the phraseology and terminology employed herein are for the purpose of description and should not be regarded as limiting, unless the specification specifically so limits the invention. Finally, the disclosure that follows is intended to apply to all alternatives, modifications and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims.